Agnostics are much nicer to be around than atheists. Agnostics are the "don't give a shit" ones. Atheism is a specific belief that there is no higher power. Agnostics tend to be chill about religion, tolerant of different beliefs and will often be willing to enthusiastically entertain religious discussions or even dive deep into theology as an academic interest.
A lot of atheists are like vegans. You'll know you've met one because they'll make sure to tell you. In majority Christian societies, they're loud and militant, using whatever legal means they can as a cudgel to smack Christians around. They routinely claim to know the bible better than most Christians, but that's usually bullshit -- they'll have memorized a few "lol look at this evil shit" verses and citations they regurgitate in any bickering with a Christian. Usually just enough to bring that meme to life -- "I don't believe in any of this shit but I'm going to hold you to these standards."
Of course in muslim countries, atheists know to keep their fucking mouths shut because unlike Christians who are willing to turn the other cheek, muzzies don't even remotely tolerate that shit. The penalty in islam for apostasy (leaving the faith) is death, but the penalty for atheism (openly denying and challenging the faith) is hyper ultra mega turbo death in the most painful ways they can imagine. They won't hesitate to tear you apart for smugly informing them that their god is bullshit. Atheists are only lippy when they live somewhere where it's safe to shit-talk.